This invention relates to spectroscopic accessories for analysis of samples by various reflectance techniques, and in particular to such accessories equipped with a microscope.
The referenced copending application describes an optical accessory for analysis of samples by internal reflection spectroscopy, the contents of which are hereby incorporated by reference. A feature of the accessories in that case is a small sampling surface located at the flat top of a hard hemisphere. The analyzing radiation--which for this accessory is in the spectral range from near to far infrared--enters the curved hemisphere surface and is focussed to a very small active area, typically 1 mm or less in size, at the top of the sampling surface. This irradiated area, referred to as the active sampling area, is often referred to as the "hot spot". A sample pressed down hard on the top sampling surface over the hot spot will interact with the radiation as is well known in internal reflection spectroscopy (IRS), modulate the radiation, which internally reflects from the sampling surface, exits the hemisphere, and ultimately is directed to the spectrometer for detection and processing into the usual spectra. A feature of this accessory is that small samples and small areas of large samples can be analyzed under high pressure with good signal-to-noise ratios providing excellent spectra despite the relatively low interaction level. However, a problem that can arise is that the precise area of the sample to be analyzed may not be located over the hot spot because of its small size.